Linguist here. I work on a daily basis with accountants (that's not their title, but let's say it is for the sake of argument or agreement); they help manage the money end of my projects, and a bunch of other projects. If we were dealing with one project, then a spreadsheet would be fine. But we're dealing with scores of projects, not to mention payroll (with individuals being paid off of from one to ten of those projects), and then there's all the taxation details that you guys know about. All this has to be tied together.
The impression from where I sit is that it's very easy to make a mistake in setting up a spreadsheet (we do have templates, but still). But an even bigger problem, it appears to me (and remember, I'm not doing this) is transferring the numbers from one spreadsheet to another. Someone needs to ensure that everyone is allocated 100% to some combination of the available projects, no more and no less, that we do the best we can at using up $ by the end of a project. (And projects do not, by and large, have identical begin/ end dates.) And each of those projects is on a separate spreadsheet, which as I say need to be tied together to ensure everyone is correctly allocated. The tying seems to be done by hand: John Doe is allocated at 37% on the project spreadsheet, so copy that '37' over to the payroll spreadsheet by hand.
Also, everything on a spreadsheet is done with labels of rows and columns: A, B, C...AA, BB...; and 1, 2, 3... I learned decades ago in computer programming 101 to use meaningful names for my variables. I don't know whether it's even possible to give meaningful labels to spreadsheet rows, columns and cells, but I can see that no one (where I work) does so. That seems to be another recipe for disaster.
In sum, it seems like a mess, and spreadsheets seem to me to be only a step above using an abacus. (Ok, a couple steps; an abacus can't print.) From where I sit, it seems like we need some kind of accounting system that ties everything together, with real names for values: something like Salary[John Doe] + Overhead[John Doe] not A1+A3.
There was an effort to move us over from spreadsheets to a real accounting system, but in the end it foundered over the cost (purchase/lease, re-training, data transfer...), and perhaps the inability to find an accounting system that worked the way we do.
If spreadsheets hadn't been invented, would we be using rational, tailorable, relatively inexpensive accounting systems?